Geological age

Molar-tooth structure (MTS) was first named in 1885 from its appearance on limestone bedding planes in the Mesoproterozoic Purcell Supergroup (= Belt Supergroup in USA.) along the border between southwestern Canada and adjacent northwestern Montana. Almost all occurrences are in Mesoproterozoic to late Neoproterozoic (Ediacaran) strata, representing a 1 billion-year time span from about 1,600 to 600 Ma, but there are several examples noted from the Paleoproterozoic and one from the Neoarchean (James et al.,
1998; Pratt,
1998b; Shields,
2002;...